New subject: Patch "v4l2: disable filesystem-dax mapping support" has been added to the 4.9-stable tree

23 Feb 2018

commit b70131de648c2b997d22f4653934438013f407a1 upstream.
V4L2 memory registrations are incompatible with filesystem-dax that
needs the ability to revoke dma access to a mapping at will, or
otherwise allow the kernel to wait for completion of DMA.  The
filesystem-dax implementation breaks the traditional solution of
truncate of active file backed mappings since there is no page-cache
page we can orphan to sustain ongoing DMA.
If v4l2 wants to support long lived DMA mappings it needs to arrange to
hold a file lease or use some other mechanism so that the kernel can
coordinate revoking DMA access when the filesystem needs to truncate
mappings.
Link: http://lkml.kernel.org/r/151068940499.7446.12846708245365671207.stgit@dwilli...
Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings")
Signed-off-by: Dan Williams dan.j.williams@intel.com
Reported-by: Jan Kara jack@suse.cz
Reviewed-by: Jan Kara jack@suse.cz
Cc: Mauro Carvalho Chehab mchehab@kernel.org
Cc: Christoph Hellwig hch@lst.de
Cc: Doug Ledford dledford@redhat.com
Cc: Hal Rosenstock hal.rosenstock@gmail.com
Cc: Inki Dae inki.dae@samsung.com
Cc: Jason Gunthorpe jgg@mellanox.com
Cc: Jeff Moyer jmoyer@redhat.com
Cc: Joonyoung Shim jy0922.shim@samsung.com
Cc: Kyungmin Park kyungmin.park@samsung.com
Cc: Mel Gorman mgorman@suse.de
Cc: Ross Zwisler ross.zwisler@linux.intel.com
Cc: Sean Hefty sean.hefty@intel.com
Cc: Seung-Woo Kim sw0312.kim@samsung.com
Cc: Vlastimil Babka vbabka@suse.cz
Cc: stable@vger.kernel.org
Signed-off-by: Andrew Morton akpm@linux-foundation.org
Signed-off-by: Linus Torvalds torvalds@linux-foundation.org
---
 drivers/media/v4l2-core/videobuf-dma-sg.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/media/v4l2-core/videobuf-dma-sg.c b/drivers/media/v4l2-core/videobuf-dma-sg.c
index 1db0af6c7f94..b6189a4958c5 100644
--- a/drivers/media/v4l2-core/videobuf-dma-sg.c
+++ b/drivers/media/v4l2-core/videobuf-dma-sg.c
@@ -185,12 +185,13 @@ static int videobuf_dma_init_user_locked(struct videobuf_dmabuf *dma,
    dprintk(1, "init user [0x%lx+0x%lx => %d pages]\n",
    	data, size, dma->nr_pages);
-	err = get_user_pages(data & PAGE_MASK, dma->nr_pages,
+	err = get_user_pages_longterm(data & PAGE_MASK, dma->nr_pages,
    		     flags, dma->pages, NULL);
if (err != dma->nr_pages) {
    	dma->nr_pages = (err >= 0) ? err : 0;
-		dprintk(1, "get_user_pages: err=%d [%d]\n", err, dma->nr_pages);
+		dprintk(1, "get_user_pages_longterm: err=%d [%d]\n", err,
+			dma->nr_pages);
    	return err < 0 ? err : -EINVAL;
    }
    return 0;

    

[4.9-stable PATCH 06/11] v4l2: disable filesystem-dax mapping support